1. Field of the Invention
The present invention relates to toner for use in an image forming apparatus such as a copier, a printer, and a facsimile, and an electrophotographic method.
2. Description of the Related Art
In electrophotographic copiers, printers, and the like, printing is performed by the following process. First, a photoreceptor is charged for forming an image. As a method for charging a photoreceptor, a corona electrical charger conventionally has been used. Recently, uniformly charging the surface of a photoreceptor by a contact type charging method has been put into practical use for the purpose of reducing the generation of ozone. According to the contact type charging method, a conductive roller is directly pressed onto a photoreceptor. In the case of a copier, after a photoreceptor is charged, an original for copying is irradiated with light. Then, the photoreceptor is irradiated with light reflected from the original through a lens system. In the case of a printer, an image signal is transmitted to a light-emitting diode, a laser diode, or the like as an exposure light source, and a latent image is formed on a photoreceptor by ON-OFF control of light. When a latent image (level of a surface potential) is formed on the photoreceptor, the latent image is developed with toner (diameter: about 5 xcexcm to about 15 xcexcm), which is previously charged coloring powder. Toner adheres to the surface of the photoreceptor in accordance with the level of a surface potential thereof, and thereafter is electrically transferred to a copying sheet. More specifically, toner is previously charged positively or negatively, and the back side of the copying sheet is charged with a polarity opposite to that of the toner, whereby the toner is attracted to the copying sheet. Hitherto, a corona electrical charger has been widely used for providing charge to the copying sheet in the same way as in charging a photoreceptor. However, in order to reduce generation of ozone, recently, a transfer apparatus using a conductive roller has been put into practical use. During transfer, all the toner on a photoreceptor is not transferred to a copying sheet. The toner partially remains on the photoreceptor. The remaining toner is scraped off by a cleaning blade or the like in a cleaning section to become waste toner. Conventionally, according to electrophotography, waste toner has been discarded without being recycled. Careless discarding should be avoided from the viewpoint of environmental protection. Recycling of waste toner poses a significant problem.
In a color copier, a photoreceptor is charged by a corona electrical charger. Thereafter, a latent image of each color is provided to the photoreceptor as a light signal, whereby an electrostatic latent image of each color is formed thereon. Then, the electrostatic latent image is developed with the first color (e.g., yellow toner) so as to become visible.
Thereafter, a transfer material charged with a polarity opposite to that of the yellow toner is brought into contact with the photoreceptor, whereby the yellow toner image formed on the photoreceptor is transferred to the transfer material. The toner remaining on the photoreceptor after transfer is cleaned, and the photoreceptor is discharged. Thus, development and transfer of the first color toner are completed.
Thereafter, the same process as that of yellow toner is repeated with respect to toner of magenta, cyan, and the like, and toner images of the respective colors are overlapped on the transfer material to form a color image. These overlapped toner images are transferred and fixed to a sheet charged with a polarity opposite to that of the toner images, whereby copying is completed.
A method for forming a color image generally includes a transfer drum method and a continuous overlapping method. According to the transfer drum method, a toner image of each color is successively formed on a single photoreceptor. Then, a transfer material wound around a transfer drum is rotated so as to repeatedly face the photoreceptor. A toner image of each color which is successively formed is transferred to the photoreceptor so as to overlap each other. According to the continuous overlapping method, a plurality of image forming sections is arranged. Then, each image forming section is passed through a transfer material transported by a belt. Thus, a toner image of each color is successively transferred to the transfer material in such a manner that color images overlap each other.
As an example using the above-mentioned transfer drum method, Japanese Laid-open Publication No. 1-252982 discloses a color image forming apparatus. FIG. 3 is a schematic view of an entire structure of the conventional example. Hereinafter, the structure and operation thereof will be described briefly.
In FIG. 3, reference numeral 501 denotes a photoreceptor. A charger 502, a developing section 503, a transfer drum 504, and a cleaner 505 are provided so as to face the photoreceptor 501. The developing section 503 includes a Y developing unit 506 for forming a yellow toner image, an M developing unit 507 for forming a magenta toner image, a C developing unit 508 for forming a cyan toner image, and a Bk developing unit 509 for forming a black toner image. All the developing units are rotated in such a manner that each developing unit successively faces the photoreceptor 501. Thus, each developing unit becomes ready for development. During operation, the transfer drum 512 and the photoreceptor 501 are rotated at a constant speed in respective arrow directions while facing each other. Reference numeral 518 denotes a toner hopper for supplying toner to a developing unit.
When an image forming operation is started, the photoreceptor 501 is rotated in the arrow direction, and the surface thereof is uniformly charged by the charger 502. Thereafter, the surface of the photoreceptor 501 is irradiated with a laser beam 510 which has been modulated with a signal for forming an image of the first color (yellow), and a latent image is formed on the surface of the photoreceptor 501. Then, the latent image is first developed by the Y developing unit 506, which faces the photoreceptor 501, to form a yellow toner image. By the time when the yellow toner image formed on the photoreceptor 501 moves to a position facing the transfer drum 504, an end of a transfer material (i.e., sheet transported from a sheet supply section 511) has been trapped by a hook 512 and wound around an outer periphery of the transfer drum 504. Thus, timing is provided in such a manner that the yellow toner image on the photoreceptor 501 faces a predetermined position of the sheet.
After the yellow toner image on the photoreceptor 501 is transferred to the sheet by a transfer charger 513, the surface of the photoreceptor 501 is cleaned by the cleaner 505, so that the surface is ready to receive a subsequent color image. Then, toner images of magenta, cyan, and black are similarly formed. At this time, the developing section 503 allows each developing unit used in accordance with color to face the photoreceptor 501, whereby each developing unit becomes ready for development. The transfer drum 504 has a size sufficient for allowing the longest sheet to wind around it and allowing developing units to be exchanged between images of respective colors.
The laser beam 510 for forming an image of each color is radiated in such a manner that a toner image of each color on the photoreceptor 501 faces a toner image which has been transferred to the sheet on the transfer drum 504 with their positions matched with each other during rotation. In this manner, toner images of four colors are overlapped and transferred to the sheet on the transfer drum 504, whereby a color image is formed on the sheet. After the toner images of all the colors are transferred, the sheet is peeled off from the transfer drum 504 by a peeling hook 514. Then, the sheet is passed through a transportation section 515 to have a toner image fixed thereon by a fixing unit 516, and output from the apparatus.
On the other hand, Japanese Laid-open Publication No. 1-250970 discloses a color image forming apparatus using a continuous transfer method. In this conventional example, for the purpose of forming images of four colors, four image forming stations each including a photoreceptor, a light-scanning unit, etc. are arranged, and a sheet transported by a belt is passed through a lower portion of each photoreceptor, whereby color toner images are overlapped.
Still furthermore, Japanese Laid-open Publication No. 2-212867 discloses another method for forming a color image by overlapping toner images of different colors on a transfer material. According to this method, a toner image of each color successively formed on a photoreceptor is first overlapped on an intermediate transfer material, and the toner images on the intermediate transfer material are transferred collectively to a transfer sheet.
As a method for permanently fixing transferred toner onto a copying sheet, a heat roll method, a pressure roll method, a flash fixing method, a method using an agent, and the like are known. Among them, the heat roll method is generally used from the viewpoint of energy efficiency, safety, and printing quality. According to this method, toner is melted on a heat roll and fixed onto a sheet.
In the case of performing the above-mentioned color printing, it is becoming necessary to satisfy characteristics required by color itself from the viewpoint of a fixing property. A color image includes several overlapped toner layers. Therefore, from the viewpoint of coloring, color reproducibility or glossiness, and transparency for an overhead projector (OHP), it is required to melt toner completely so that the surface thereof becomes flat. However, if excessively melted, toner adheres to the surface of a heat roll and is transferred to a transfer material such as a sheet transported thereafter. So-called hot offset occurs. In order to prevent hot offset, a heat roll is covered with a material such as silicone rubber and fluorocarbon resin having a satisfactory release property with respect to melted toner. Alternatively, a heat roll is coated with liquid having a satisfactory release property, such as silicone oil. Alternatively, a release component such as low molecular-weight polyethylene and low molecular-weight polypropylene is contained in the toner. The downside of these methods is that a mechanism of oil coating is complicated and an apparatus cannot be minimized. Furthermore, it is required to supply oil every predetermined period, and oil adheres to the surface of a transfer material such as a sheet. Therefore, it is required to minimize the consumption amount of oil. Furthermore, in the case where dispersibility of a release component contained in toner is poor, phenomena such as toner-filming and toner-spent occur. More specifically, this decreases toner flowability which adversely affects charge characteristics, and furthermore, the toner adheres to a photoreceptor, a toner holder, carrier, and the like to contaminate them.
As is well-known, toner for electrostatic charge development used in the above-mentioned developing methods generally contains internal additives such as a binder resin component, a colorant made of a pigment or a dye, a plasticizer, a charge control agent, and, if required, magnetic particles and a release agent, and an external additive. As the binder resin component, natural or synthetic resin is used alone or in appropriate combination. The binder resin component and the other components are previously mixed in an appropriate proportion and kneaded by heat melting, followed by fine crushing and fine classification (if required), and the external additive is added to the mixture, whereby toner is obtained.
Hitherto, paying attention to the viscoelasticity of the toner, various suggestions have been made for the purpose of enhancing a fixing property of the toner.
For example, Japanese Laid-open Publication No. 5-100477 discloses binder resin having a loss modulus Gxe2x80x3t of 1xc3x97105 dyn/cm2 or less at 150xc2x0 C. and a storage modulus Gxe2x80x2t of 2xc3x97104 dyn/cm2 or more at 200xc2x0 C., and a release agent with particular viscosity. However, due to a large value of Gxe2x80x3t, transparency for an OHP and glossiness are not enhanced.
Furthermore, Japanese Laid-open Publication No. 6-59502 discloses toner having a loss modulus Gxe2x80x3t of 104 dyn/cm2 or more at 150xc2x0 C. and an apparent viscosity of 0.1 to 5xc3x97103 Paxc2x7sec. In this structure, although resistance to hot offset is enhanced, satisfactory transparency for an OHP cannot be obtained due to a large value of Gxe2x80x3t.
Still furthermore, Japanese Laid-open Publication Nos. 2-282757 and 7-77838 make suggestions regarding a toner size distribution and dynamic viscoelasticity. However, these publications pay attention to only dynamic viscoelasticity of toner regarding transparency for an OHP. In this case, the toner is designed paying attention to transparency for an OHP, so that hot offset is likely to occur. Thus, it is required to coat a fixing heat roll with a great amount of release oil such as silicone oil for the purpose of preventing hot offset.
Still furthermore, Japanese Laid-open Publication Nos. 2-190868 and 9-304965 describe the smoothness of a fixing surface. However, only dynamic viscoelasticity of toner and characteristics of binder resin are paid attention to, so that high transparency for an OHP and resistance to hot offset cannot be obtained simultaneously.
In the case where a release agent such as wax is added to toner for the purpose of preventing hot offset, when an added amount of the release agent is small, satisfactory effects cannot be obtained. Moreover, due to poor dispersibility of the release agent, toner flowability is decreased, and toner-filming and toner-spent occur. Specifically, an aggregated or liberated release agent adheres to a photoreceptor, a toner holder, and carrier to contaminate them.
Furthermore, while printing is repeated, toner with a particular size may be selectively developed. Since toner has size distribution, this phenomenon occurs due to the difference in flowability of individual particles, the difference in aggregation of toner, or variation of a composition.
When there is a great difference in flowability of individual toner particles, toner particles are variously charged by friction. This causes a variation in the amount of charge. In the case where toner having a particular size is selectively developed, size distribution of the toner which has remained without being developed changes, which decreases image density and increases fog. Furthermore, transfer efficiency is decreased, so that the smoothness of the surface of an image is decreased. As a result, transparency after fixing will not be enhanced.
Therefore, with the foregoing in mind, it is an object of the present invention to provide toner which realizes satisfactory transparency for an OHP, glossiness, and resistance to hot offset, which allows a high quality image to be formed, keeping high density and less fog for a long period of time, and which is capable of preventing toner-filming with respect to a photoreceptor, by specifying dynamic viscoelasticity of toner to improve the smoothness of an image surface. It is another object of the present invention to provide an electrophotographic method using the toner.
Toner of the present invention at least includes binder resin, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa), and the toner contains 5 to 50% by number of toner particles with a size of 2xc3x9710xe2x88x926 to 5xc3x9710xe2x88x926 m in size distribution of the toner.
Toner of the present invention at least includes binder resin, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa), and a compression ratio C calculated from a static density of the toner and a dynamic density thereof satisfies 5xe2x89xa6C(%)xe2x89xa640.
Toner of the present invention at least includes binder resin, wax, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), and a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa).
Toner of the present invention at least includes binder resin, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa), the toner contains 5 to 50% by number of toner particles with a size of 2xc3x9710xe2x88x926 to 5xc3x9710xe2x88x926 m in size distribution of the toner, and a compression ratio C calculated from a static density of the toner and a dynamic density thereof satisfies 5xe2x89xa6C(%)xe2x89xa640.
Toner of the present invention at least includes binder resin, wax, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa), and the toner contains 5 to 50% by number of toner particles with a size of 2xc3x9710xe2x88x926 to 5xc3x9710xe2x88x926 m in size distribution of the toner.
Toner of the present invention at least includes binder resin, wax, a colorant, and an external additive, wherein a storage modulus Gxe2x80x2r (frequency: 10 rad/s) of the binder resin at 190xc2x0 C. and a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 0.15xe2x89xa6Log10(Gxe2x80x2t/Gxe2x80x2r)xe2x89xa62, a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), and a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa).
Toner of the present invention at least includes binder resin, wax, a colorant, and an external additive, wherein a storage modulus Gxe2x80x2r (frequency: 10 rad/s) of the binder resin at 190xc2x0 C. and a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfy 0.15xe2x89xa6Log10(Gxe2x80x2t/Gxe2x80x2r)xe2x89xa62, a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa), and a compression ratio C calculated from a static density of the toner and a dynamic density thereof satisfies 5xe2x89xa6C(%)xe2x89xa640.
In one embodiment of the present invention, the above-mentioned toner is used for electrophotography at least including: making visible an electrostatic latent image on a photoreceptor by developing it with a two-component developer containing the toner of claim 1 and carrier; transferring the visible toner on the photoreceptor to a transfer sheet; and cleaning the photoreceptor by removing the toner, which has partially remained on the photoreceptor during the transfer, from the photoreceptor, wherein a relationship Dcxc3x97TD/Dv of a volume average size Dc (m) of the carrier, a volume average size Dv (m) of the toner, and a mixed ratio TD between the carrier and the toner is 0.20 to 0.45.
In another embodiment of the present invention, the above-mentioned toner includes the colorant in an amount of 2 to 15 parts by weight based on 100 parts by weight of the binder resin.
In another embodiment of the present invention, the above-mentioned toner includes the wax in an amount of 0.5 to 10 parts by weight based on 100 parts by weight of the binder resin.
In another embodiment of the present invention, an endothermic peak of the wax measured by DSC is 65xc2x0 C. to 90xc2x0 C.
In another embodiment of the present invention, the wax comprises at least one selected from the group consisting of carnauba wax, candelilla wax, hydrogenated jojoba oil, rice wax, hydrogenated lanolin, meadowfoam oil, bees wax, ceresin wax, and derivatives thereof.
An electrophotographic method of the present invention includes: making visible an electrostatic latent image on a photoreceptor by developing it with toner which includes binder resin, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa), and the toner contains 5 to 50% by number of toner particles with a size of 2xc3x9710xe2x88x926 to 5xc3x9710xe2x88x926 m in size distribution of the toner; transferring the visible toner on the photoreceptor to a transfer sheet; cleaning the photoreceptor by removing the toner, which has partially remained on the photoreceptor during the transfer, from the photoreceptor; and returning waste toner removed by the cleaning and re-cycling it.
In one embodiment of the present invention, a compression ratio C calculated from a static density of the toner and a dynamic density thereof satisfies 5xe2x89xa6C(%)xe2x89xa640.
In another embodiment of the present invention, the toner further includes wax.
An electrophotographic method of the present invention includes: making visible an electrostatic latent image on a photoreceptor by developing it with toner which includes binder resin, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa), and a compression ratio C calculated from a static density of the toner and a dynamic density thereof satisfies 5xe2x89xa6C(%)xe2x89xa640; transferring the visible toner on the photoreceptor to a transfer sheet; cleaning the photoreceptor by removing the toner, which has partially remained on the photoreceptor during the transfer, from the photoreceptor; and returning waste toner removed by the cleaning and re-cycling it.
An electrophotographic method of the present invention includes: making visible an electrostatic latent image on a photoreceptor by developing it with toner which includes binder resin, wax, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), and a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa); transferring the visible toner on the photoreceptor to a transfer sheet; cleaning the photoreceptor by removing the toner, which has partially remained on the photoreceptor during the transfer, from the photoreceptor; and returning waste toner removed by the cleaning and re-cycling it.
In one embodiment of the present invention, a storage modulus Gxe2x80x2r (frequency: 10 rad/s) of the binder resin at 190xc2x0 C. and a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 0.15xe2x89xa6Log10(Gxe2x80x2t/Gxe2x80x2r)xe2x89xa62.
In another embodiment of the present invention, a compression ratio C calculated from a static density of the toner and a dynamic density thereof satisfies 5xe2x89xa6C(%)xe2x89xa640.
An electrophotographic method of the present invention includes: making visible an electrostatic latent image formed on an image holder by developing it with toner which includes binder resin, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies :100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa), and the toner contains 5 to 50% by number of toner particles with a size of 2xc3x9710xe2x88x926 to 5xc3x9710xe2x88x926 m in size distribution of the toner; primary-transferring the toner to an endless intermediate transfer body, which is in contact with the image holder; forming an overlapped image of the transferred toner by performing the primary-transfer a plurality of times; and secondary-transferring the overlapped image of the transferred toner, which has been formed on the intermediate transfer body, collectively to an image receiving sheet transported from a sheet supply side.
In one embodiment of the present invention, a compression ratio C calculated from a static density of the toner and a dynamic density thereof satisfies 5xe2x89xa6C(%)xe2x89xa640.
In another embodiment of the present invention, the toner further includes wax.
An electrophotographic method of the present invention includes: making visible an electrostatic latent image formed on an image holder by developing it with toner which includes binder resin, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa), and a compression ratio C calculated from a static density of the toner and a dynamic density thereof satisfies 5xe2x89xa6C(%)xe2x89xa640; primary-transferring the toner to an endless intermediate transfer body, which is in contact with the image holder; forming an overlapped image of the transferred toner by performing the primary-transfer a plurality of times; and secondary-transferring the overlapped image of the transferred toner, which has been formed on the intermediate transfer body, collectively to an image receiving sheet transported from a sheet supply side.
An electrophotographic method of the present invention includes: making visible an electrostatic latent image formed on an image holder by developing it with toner which includes binder resin, wax, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa); primary-transferring the toner to an endless intermediate transfer body, which is in contact with the image holder; forming an overlapped image of the transferred toner by performing the primary-transfer a plurality of times; and secondary-transferring the overlapped image of the transferred toner, which has been formed on the intermediate transfer body, collectively to an image receiving sheet transported from a sheet supply side.
In one embodiment of the present invention, a storage modulus Gxe2x80x2r (frequency: 10 rad/s) of the binder resin at 190xc2x0 C. and a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 0.15xe2x89xa6Log1(Gxe2x80x2t/Gxe2x80x2r)xe2x89xa62.
In another embodiment of the present invention, a compression ratio C calculated from a static density of the toner and a dynamic density thereof satisfies 5xe2x89xa6C(%)xe2x89xa640.
An electrophotographic method of the present invention includes: making visible an electrostatic latent image formed on an image holder by developing it with toner which includes binder resin, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa), and the toner contains 5 to 50% by number of toner particles with a size of 2xc3x9710xe2x88x926 to 5xc3x9710xe2x88x926 m in size distribution of the toner; primary-transferring the toner to an endless intermediate transfer body, which is in contact with the image holder; cleaning the photoreceptor by removing the toner, which has partially remained on the photoreceptor during the primary-transfer, from the photoreceptor; returning waste toner removed by the cleaning to development and recycling it; forming an overlapped image of the transferred toner by performing the primary-transfer a plurality of times; and secondary-transferring the overlapped image of the transferred toner, which has been formed on the intermediate transfer body, collectively to an image receiving sheet transported from a sheet supply side.
In one embodiment of the present invention, a compression ratio C calculated from a static density of the toner and a dynamic density thereof satisfies 5xe2x89xa6C(%)xe2x89xa640.
In another embodiment of the present invention, the toner further includes wax.
An electrophotographic method of the present invention includes: making visible an electrostatic latent image formed on an image holder by developing it with toner which includes binder resin, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa), and a compression ratio C calculated from a static density of the toner and a dynamic density thereof satisfies 5xe2x89xa6C(%)xe2x89xa640; primary-transferring the toner to an endless intermediate transfer body, which is in contact with the image holder; cleaning the photoreceptor by removing the toner, which has partially remained on the photoreceptor during the primary-transfer, from the photoreceptor; returning waste toner removed by the cleaning to development and recycling it; forming an overlapped image of the transferred toner by performing the primary-transfer a plurality of times; and secondary-transferring the overlapped image of the transferred toner, which has been formed on the intermediate transfer body, collectively to an image receiving sheet transported from a sheet supply side.
An electrophotographic method of the present invention includes: making visible an electrostatic latent image formed on an image holder by developing it with toner which includes binder resin, wax, a colorant, and an external additive, wherein a loss modulus Gxe2x80x3t (frequency: 10 rad/s) of the toner at 170xc2x0 C. satisfies 100xe2x89xa6Gxe2x80x3txe2x89xa65000 (Pa), a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 10xe2x89xa6Gxe2x80x2txe2x89xa63000 (Pa); primary-transferring the toner to an endless intermediate transfer body, which is in contact with the image holder; cleaning the photoreceptor by removing the toner, which has partially remained on the photoreceptor during the primary-transfer, from the photoreceptor; returning waste toner removed by the cleaning to development and recycling it; forming an overlapped image of the transferred toner by performing the primary-transfer a plurality of times; and secondary-transferring the overlapped image of the transferred toner, which has been formed on the intermediate transfer body, collectively to an image receiving sheet transported from a sheet supply side.
In one embodiment of the present invention, a storage modulus Gxe2x80x2r (frequency: 10 rad/s) of the binder resin at 190xc2x0 C. and a storage modulus Gxe2x80x2t (frequency: 10 rad/s) of the toner at 190xc2x0 C. satisfies 0.15xe2x89xa6Log10(Gxe2x80x2t/Gxe2x80x2r)xe2x89xa62.
In another embodiment of the present invention, a compression ratio C calculated from a static density of the toner and a dynamic density thereof satisfies 5xe2x89xa6C(%)xe2x89xa640.
As described above, the toner of the present invention has particular viscoelasticity, size distribution, and compression ratio. Therefore, the toner smooths unevenness of an image surface, and allows a decrease in the amount of silicone oil to be provided to a fixing heat roller because of satisfactory dispersibility of a colorant. Furthermore, high transparency for an OHP with high glossiness can be maintained for a long period of time, and hot offset can be prevented. High image quality with high density and less fog can be realized, and toner-filming can be prevented with respect to a photoreceptor.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.